1. Field of the Invention
This invention relates to the production and use of a family of purpurins, a family of chlorins and metal complexes of the purpurins and chlorins, and to purpurin- and chlorin-containing compositions. The purpurins have a reduced pyrrole ring and an unsaturated isocyclic ring fused to a pyrrole ring; the unsaturated isocyclic ring of the purpurins corresponds with a saturated ring in the chlorins. The chlorins are useful as green dyes. The chlorins and the purpurins are useful in the detection and treatment of tumors; after they have been administered systemically, e.g., intravenously, they localize preferentially in a tumor. After they have been administered, and have localized in a tumor, their presence can be detected by illumination with ultra violet light, which causes them to fluoresce. The chlorins and purpurins of the invention can also be used to treat tumors; after they have been administered and have localized, irradiation with light of a wave length at which they show an absorbance peak causes a reaction which damages or destroys the tumor where they have localized. The purpurin- and chlorin-containing compositions are solutions thereof in an organic liquid that is physiologically acceptable for intravenous or topical administration and emulsions or suspensions of such solutions and water or saline or other solutions.
2. The Prior Art
Four purpurins having an unsaturated isocyclic ring fused to a reduced pyrrole ring are known to be reported in the prior art, a communication to the editor by Woodward et al., JACS, Vol. 82, pp. 3800 et seq., 1960, where they are disclosed as intermediates in the synthesis of chlorophyll, and journal articles by Witte et al., Angew, Chem. Internat. Edit./Vol. 14, No. 5, pp. 361 et seq., 1975, and Arnold et al., Journal of the Chemical Society, Perkin Transactions I, pp. 1660 et seq., 1979. No utility for purpurins is suggested by either Witte et al. or Arnold et al. In addition European patent application EP142,732 (C.A. 103: 123271S) discloses certain chlorins of a different family and that they accumulate preferentially in cancer cells removed from hamsters that had been infected with pancreatic cancer.
Purpurins and chlorins are similar in structure to porphyrins. One porphyrin, called protoporphyrin IX, can be separated from blood. Hematoporphyrin can be produced from protoporphyrin IX; a chemical mixture derived from hematoporphyrin, called hematoporphyrin derivative, and often abbreviated "HpD", can be administered intravenously and used in the manner described above for the detection and treatment of tumors. The exact composition of HpD, however, is not known; in fact, it is a mixture of many different porphyrins and related compounds (see, for example, Porphyrin Photosensitization, edited by David Kassel and Thomas J. Dougherty, Plenum Press, New York and London, 1983, pp. 3-13). As a consequence, the chlorins and purpurins of the instant invention are preferred over HpD for this use because they are single, known compounds. In addition, the chlorins and purpurins have absorbance peaks at longer wavelengths and show greater absorbances, by comparison with HpD; the longer wavelength peaks are advantageous because light of the longer wavelengths is capable of greater penetration of tissue, while the greater absorbances are desirable because less light energy is required to cause a given degree of reaction.